Output: Add value if not exists Loop through the array to check whether a particular username value already exists and if it does do nothing, but if it doesn’t add a new object to the array. const arr = [{ id: 1, username: 'fred' }, { id: 2, username: 'bill' }, { ...
//code to check if a value exists in an array using javascript for loop var fruits_arr = ['Apple', 'Mango', 'Grapes', 'Orange', 'Fig', 'Cherry']; function checkValue(value, arr) { var status = 'Not exist'; for (var i = 0; i < arr.length; i++) { var name = arr[...
varfruits=["Apple","Banana","Mango","Orange","Papaya"];// Check if a value exists in the fruits arrayif(fruits.indexOf("Mango")!==-1){alert("Value exists!")}else{alert("Value does not exists!")} ES6 has introduced theincludes()method to perform this task very easily. But, ...
constobj={name:'Alice',age:30,city:'New York'};// 使用 for...in 循环遍历for(letkeyinobj){if(obj.hasOwnProperty(key)){console.log(`Key:${key}, Value:${obj[key]}`);}}// 使用 Object.keys() 遍历Object.keys(obj).forEach(key=>{console.log(`Key:${key}, Value:${obj[key]}`...
functionexists(value, array){returnarray.some(e=>e === value);} letmarks = [4,5,7,9,10,2]; console.log(exists(4, marks));console.log(exists(11, marks)); 输出: truefalse 2) 检查一个数组是否有一个元素...
let apiResponse = fetch("https://fjolt.com/api").then(res => res.json()).then((data) => { return data;});// Now contains a JSON object - assuming one exists1.2.3.4.JavaScript Fetch 的选项 由于Fetch 可以发送和接收 HTTP 请求,当我们想要使用它获取 URL数据的时候,还可以带一些选项,即...
它是用三点(...)表示,Array是可以扩展的,如果是Object,会按照key-value进行扩展。 代码语言:javascript 代码运行次数:0 运行 AI代码解释 conststuendts=['Angel','Ryan'];constpeople=['Sara',...stuendts,'Kelly','Eason'];conslog.log(people);// ["Sara", "Angel", "Ryan", "Kelly", "Eason"]...
functionexists(value){returnx!=null?Promise.resolve(value):Promise.reject(`Invalid value:${value}`)}asyncfunctionfoo(num){returnexists(num).then(v=>23*v)} 通过这种方式就可以把来自exists中的catch方法委派到调用foo的函数中: 代码语言:javascript ...
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Thehas()method returnstrueif a specified value exists in a set. Example // Create a Set constletters =newSet(["a","b","c"]); // Does the Set contain "d"? answer = letters.has("d"); Try it Yourself » The forEach() Method ...